In a mold clamping device of an injection molding device or a die-casting machine, a fixed mold platen and a movable mold platen are disposed to face each other, and the movable mold platen is moved forward and backward by an actuator such as a hydraulic cylinder so as to approach and move away from the fixed mold platen. Further, a fixed mold is attached to the fixed mold platen, and a movable mold is attached to the movable mold platen. A resin or a metal is injected into a cavity formed between the fixed mold and the movable mold, which results in a molded article in a predetermined shape.
The injection molding device and the die-casting machine each include a large fixed mold platen and a large movable mold platen corresponding to a dimension of a mold. To produce a large molded article, the mold platen is also inevitably increased in size. Note that each of the fixed mold platen and the movable mold platen is also referred to as a mold platen except for a case where it is necessary to distinguish the fixed mold platen and the movable mold platen.
To increase the size of the mold platen, it is necessary to reinforce the mold platen in order to prevent deformation of the mold platen particularly on mold attachment surface side. As an example of mold platen reinforcement, for example, a structure in which a rib is provided on rear surface side of the mold platen opposite to the mold attachment surface disclosed in Patent Literature 1 and a structure in which the mold platen is formed in a box shape and a rib is provided inside the mold platen disclosed in Patent Literature 2 are well-known.
The mold platen disclosed in Patent Literature 2 includes an outer peripheral reinforcing rib that is provided between a mold plate and a rear-surface plate and is provided between coupling portions adjacent to each other along outer peripheries of the mold plate and the rear-surface plate. An asymmetrical opening is provided in the outer peripheral reinforcing rib, which achieves weight reduction while maintaining sufficient strength.